Power transmission chains are widely used in the automotive industry not only for ignition timing, but also for transferring mechanical power to the driving wheels of a vehicle. Two types of power transmission chains are traditional roller chains and the so-called “silent chains”. Both roller chains and silent chains use steel pins as important components.
During assembly and subsequent operation of a vehicle, the steel pins are subject to wear. To improve the wear resistant properties of the steel substrates, a hard coating may be applied to the steel substrate. For example, vanadium carbide (VC) coatings have been placed on small steel parts such as pins to improve wear resistance. The composition of the pin substrate steel, however, may have a significant effect on vanadium coated steel pins. For example, steel substrate materials having about 1.5 weight percent or less of chromium is thought to not form enough diffusion of carbide at the vanadium carbide coating/steel interface, which may result in poor adhesion of the vanadium carbide coating to the steel substrate.
It has been found that appropriate carbon content of the substrate steel can ensure the thickness of the VC coating and impart strength and hardness, and appropriate chromium content in the substrate steel is important for good adhesion of the coating to the substrate steel pins.
As a solution, pins having a hard chromium carbide layer can be made by depositing the chromium from FeCr powder surround the pin surface at 970 degrees Celsius. However, the use of ferro-chromium and elemental chromium powders is frequently foreclosed or inhibited by environmental regulation.